It has been known heretofore to provide a dental handpiece with a coolant under pressure such as air and/or water. German Auslegeschrift No. 1,098,162 for example, discloses a dental handpiece of this character wherein a cooling air line is fed by the exhaust air of a pressure air turbine mounted within the head thereof.
Generally, handpieces of the type described are subjected to the action of the coolant medium, such as air and/or water, under a predetermined pressure. On occasion the pressure in the coolant air line and/or in the cooling water line may fluctuate. The cause of this may, for example, be due to a decrease in the propelling air pressure and this may result in the decrease in cooling air pressure. This may occur due to a defect in the compressor installation or, alternatively, due to the intentional adjustment of the propelling air quantity in connection with regulation of the turbine speed. If, as a consequence thereof, the pressure in the cooling air line falls below that in the cooling water line, the water being introduced via the cooling water line may be displaced into the cooling air line with the result that this water may cause damage to the rotating turbine or to the compressor installation. Also, the desired spray of air and water from the outlet nozzle, may be interrupted or otherwise affected. The resultant effluent may simply be a discharge of water at a reduced pressure.
It will thus be seen that one of the problems existent with dental handpieces currently available has been in insuring the maintenance of the desired spray of air and water from the outlet nozzle or nozzles despite fluctuations in pressure in the air and/or water lines. It has also been a problem in devising the arrangement of gaseous and liquid coolant lines such that the liquid, i.e. water, is prevented from entering the gaseous coolant, i.e., air line or vice versa since these appear to be common causes of impairment of the flow of air and water from the discharge nozzles.